Alternative synthesis of structurally defective MoS₂ nanoflakes for efficient hydrogen evolution reaction

Two-dimensional layered molybdenum sulfide (MoS₂) is highly attractive as electrocatalyst for high purity hydrogen production because of its intrinsic properties and favorable cost-benefit ratio. Notably, electrocatalytic activity of MoS₂ strongly depends on exposed edges and density of defect sites. Here, we report the preparation of MoS₂ nanoflakes through an oxalic acid assisted-hydrothermal method. A comparatively excessive amount of oxalic acid was used as an alternative strategy for the preparation of MoS₂. XRD, TEM, RAMAN, and XPS results revealed that as-prepared MoS₂ is highly defective with presence of unsaturated S and abundant exposed edges. As a result, structurally defective MoS₂ nanoflakes exhibit high activity for HER with low overpotential of 214 mV at 10 mA/cm², a small Tafel slope of 52 mV/decade and excellent stability.